Field of the Invention
The present invention relates to a zoom lens and an image pickup apparatus including the same, which are suitable for an image pickup optical system used in an image pickup apparatus using an image pickup element, for example, a video camera, an electronic still camera, a broadcasting camera, or a monitoring camera, or an image pickup apparatus, for example, a silver halide film camera.
Description of the Related Art
In recent years, it is demanded for image pickup optical systems that are used in image pickup apparatus to be zoom lenses having a high zoom ratio and high optical characteristics over an entire zoom range thereof while being small as a whole. Further, it is also demanded for such image pickup optical systems to have small aberration variation during focusing, and high optical characteristics over an entire object distance thereof.
As a zoom lens capable of easily achieving a high zoom ratio, there has been known a positive lead type zoom lens in which a lens unit having a positive refractive power is arranged closest to an object side. In order to provide a positive lead type zoom lens having small aberration variation during focusing, and high optical characteristics over an entire object distance thereof, there has been known a zoom lens employing a floating system in which two lens units are configured to move during focusing.
In Japanese Patent Application Laid-Open No. 2011-180218, there is disclosed a zoom lens including, in order from an object side to an image side, a first lens unit to a fifth lens unit having positive, negative, negative, positive, and negative refractive powers, in which the third lens unit and the fifth lens unit are configured to move in opposite directions, to thereby perform focusing.
In Japanese Patent Application Laid-Open No. 2013-109013, there is disclosed a zoom lens including, in order from an object side to an image side, a first lens unit to a seventh lens unit having positive, negative, positive, positive, negative, positive, and negative refractive powers, in which the fifth lens unit and the sixth lens unit are configured to move in opposite directions, to thereby perform focusing.
In order to reduce aberration variation due to focusing, it is effective to employ a floating system in which a plurality of lens units are configured to move in an optical axis direction during focusing. With the use of the floating system, the movement amount of a focusing unit for focusing at close distance can be reduced, and hence aberration variation is easily reduced while an entire lens system is downsized. In particular, it is easy to perform focusing at close distance, which can be regarded as macro photography, while reducing aberration variation.
In order to provide a positive lead type zoom lens having a high zoom ratio and high optical characteristics over an entire zoom range and an entire object distance thereof while downsizing the entire system, it is important to appropriately set elements that form the zoom lens. It is important to appropriately set, for example, a zoom type (the number of lens units, the refractive power of each lens unit, movement conditions during zooming, or the like), selection of a lens unit configured to move during focusing, and the lens configuration of the lens unit configured to move during focusing.